The invention relates generally to ammunition magazines, and, more particularly, to a chain tightener for an ammunition magazine.
Ammunition magazines of the type disclosed herein are generally known from EP-078 482 B1. In that document, ammunition is transported by an endless ammunition guide chain in several loops which are guided around deflection rollers through the ammunition magazine. A tension spring acts on one of the deflection rollers. This tension spring forces the loop guided around this deflection roller outward, so that the ammunition guide chain is tightened during a clamping movement of this spring (i.e., disengagement movement), whereas it is released during a movement of the spring opposite its direction of tightening (i.e., engagement movement).
A drawback of this tightening system lies in the fact that the spring force can be overcome during acceleration of the ammunition guide chain, such that the spring engages and the ammunition guide chain is, consequently, released. This ability to overcome the spring force is primarily due to the fact that the spring constant must be dimensioned correspondingly low. If the tightening force exerted by the spring changes during heat-related material expansions, when the ammunition guide chain engages or disengages according to the expansion movements, the resulting tightening force of the spring must not be too strong or too weak, so that the material of the ammunition guide chain is not stressed too strongly.
An ammunition magazine with a beltless fed, endless ammunition guide chain is also known from DE-36 44 513 C2. In that reference, two opposite short loops of the ammunition guide chain, (one of which is coupled to an ammunition transfer device), are guided to move in the direction of transport. The displacement movement is supported by a prestressed gas pressure spring. The drive unit of the ammunition guide chain is situated in this short loop with the connected ammunition transfer device, so that during acceleration or braking of the ammunition guide chain, initially only the inert mass of the short loop must be moved. Movement of the rest of the ammunition guide chain is only disengaged once by the displaceable loops. Short acceleration times with comparatively weakly dimensioned drive units can thus be achieved. However, this document does not describe the tightener in detail, with which the chain tension of the ammunition guide chain can be adjusted.
A similar principle is known from U.S. Pat. 4,573,395, in which a short bend is disconnected from the movement of the rest of the ammunition guide chain. In this case, however, two loops of this bend do not lie opposite each other and are not guided to move in the direction of feed, but lie parallel to each other and are connected over the two ends of a rocker. The two parallel loops therefore always execute oppositely directed movements via this rigid motion coupling.
A shortcoming of the known ammunition magazines with chain tighteners is that the chain tightener executes engagement or disengagement movements, especially during acceleration or braking of the ammunition guide chain, in which mostly undesired slack can occur in the ammunition guide chain.
In accordance with an aspect of the invention, an ammunition magazine is disclosed for use with beltless fed ammunition. The ammunition magazine includes an endless, guided ammunition guide chain to convey ammunition within the magazine. It also includes a chain tightener having a spring constant and being operatively coupled to the ammunition guide chain. The chain tightener executes a movement in a direction of tightening to increase chain tension in at least a portion of the guide chain and executes a movement opposite the direction of tightening to reduce chain tension in at least a portion of the guide chain. The ammunition magazine also includes means for effectively adjusting the spring constant of the chain tightener as a function of the direction of movement of the chain tightener and as a function of a speed of movement of the chain tightener.
In accordance with another aspect of the invention, an ammunition magazine is disclosed. The ammunition magazine includes an ammunition guide chain to convey ammunition within the magazine. It also includes a chain tightener having a spring constant and being operatively coupled to the guide chain. The chain tightener executes a movement in a first direction to increase chain tension in at least a portion of the guide chain and executes a movement in a second direction substantially opposite the first direction to reduce tension in at least a portion of the guide chain. The ammunition magazine further includes a brake cooperating with the chain tightener to effectively increase the spring constant of the chain tightener in response to forces which, in the absence of the brake, would move the chain tightener in the second direction at a speed above a predetermined threshold.
In accordance with still another aspect of the invention, an ammunition magazine is provided. The ammunition magazine includes an ammunition guide chain to convey ammunition within the magazine and a chain tightener. The chain tightener has a spring constant and is operatively coupled to the guide chain. The chain tightener executes a movement in a first direction to increase chain tension in at least a portion of the guide chain and executes a movement in a second direction substantially opposite the first direction to reduce tension in at least a portion of the guide chain. The ammunition magazine is also provided with a brake operatively coupled to the chain tightener. The brake substantially prevents movement of the chain tightener in the second direction at speeds above a first predetermined threshold, but the brake does not substantially interfere with (a) movement of the chain tightener in the first direction and (b) movement of the chain tightener in the second direction at speeds below a second predetermined threshold.
In accordance with still another aspect of the invention, an ammunition magazine is provided for use with beltless fed ammunition. The ammunition magazine includes an endless, guided ammunition guide chain to convey ammunition within the magazine. It also includes a chain tightener having a spring constant and being operatively coupled to the ammunition guide chain. The chain tightener executes a movement in a direction of tightening to increase chain tension in at least a portion of the guide chain and executes a movement opposite the direction of tightening to reduce chain tension in at least a portion of the guide chain. The magazine further includes a hydraulic cylinder at least functionally coupled in parallel to the chain tightener to effectively adjust the spring constant of the chain tightener as a function of the direction of movement of the chain tightener and as a function of a speed of movement of the chain tightener. The hydraulic cylinder includes a return valve which opens when the chain tightener moves in the direction of tightening.
Other features and advantages are inherent in the apparatus claimed and disclosed or will become apparent to those skilled in the art from the following detailed description and its accompanying drawings.